One problem faced when using information handling systems, including database systems, is loss of data written to disk. One cause of disk data loss is known as the interrupted write problem. After an interrupted write, only a portion of the data sent to the disk is written correctly. Interrupted writes may occur during software or hardware initiated restart operations. This situation is problematic because the information handling system may not know that the data was not written successfully, because no processes are running to receive an error message reporting the failed write or an error message was not generated.
One system for handling interrupted writes is a Write Ahead Logging (WAL) system. In general, a WAL system logs write commands that are sent to a disk. In the event of a restart operation, the log is played back to synchronize the disk. In some WAL systems a log of all disk writes is replayed to reconstruct the disk after a failed write.
One method for handling interrupted writes is to disallow in-place writes (e.g., writing over a previous version of data block with a new version of a data block). Disallowing in-place writes provides at least one complete copy of a data block, that is, either the previous version of the data block, the new version of the data block, or possibly both copies of the data block will be intact at any time in the event of an interrupted write.